The present invention relates to the preparation of block copolymers comprising a first polyolefin block and at least one second polar or nonpolar polymer block and the products obtained therefrom.
Block copolymers combining a polyolefin block with a polyethylene-like polymer block are useful as compatibilizers for blends of e.g. polyethylene (PE) and other polyolefins (e.g. iPP). The preparation of actual polyolefin-PE block copolymers (e.g. iPP-b-PE) is a very tedious process that requires a living catalyst or a chain transfer polymerization process including intermediate venting steps to produce block copolymers consisting of well-defined iPP and PE blocks.
Block copolymers combining a polyolefin block with at least one polar polymer block may be used to enhance the properties of polyolefin polymers that have an inherent nonpolar character that leads to drawbacks for certain applications, because of poor adhesion, printability and compatibility that can restrict their efficacy. Furthermore, block copolymers combining a polyolefin block with a polar polymer block are useful as compatibilizers for blends of e.g. polyolefins (e.g. iPP) and polar polymers (e.g. polyester or polycarbonate).
In the prior art different approaches have been reported for the preparation of polyolefin-based block copolymers, based on either living catalysts or chain transfer concepts for polymerizations mediated by homogeneous single-site catalysts, being a metal catalyst that consists of solely one type of catalytically active site. The prior art describes the preparation of chain-end functionalized polyolefins in a separate process, which are subsequently used as initiators for forming the corresponding block copolymers using an additional catalyst.
WO 2011/014533 of Dow Global Technologies discloses the use of a multifunctional chain transfer agent that can be used in preparing polyethylene-b-caprolactone block copolymers.
Other prior art documents (e.g. Han, Macromolecules, 2002, 35, 8923-8925; and Chung et al. Polymer 2005, 46, 10585-10591) use a process, which goes via a polyolefin-OH intermediate compound. This includes intermediate isolation, purification and drying of said functional polyolefin. Subsequent ring-opening polymerization reaction (ROP) is carried out using a catalyst system.
Other, related prior art (Becquart, Macromol. Mater. Eng. 2009, 294, 643-650) uses a process where poly(ethylene-co-vinyl alcohol) (EVOH) is applied as a poly(hydroxyl) functionalized polyethylene and treated with a polyester in the presence of SnOct2 as transesterification catalyst to form the corresponding EVOH-graft-polyester graft copolymers.
For example, polyolefin-polar or polyolefin-nonpolar block copolymers can be obtained by first preparing two separate blocks and subsequently coupling these blocks. Another way of preparing them consists of using a polyolefin having a functional end group as initiator to grow a polar or nonpolar polymer from it.
It is an aim of the present invention to provide a catalyst system allowing efficient chain transfer in the preparation of metal functionalized polyolefins, which after oxidation of the metal-functionalized polyolefins which can be applied as catalytic initiators for the formation of polyolefin-based block copolymers.
It is moreover an aim of the present invention to produce A-B or A-B-C- . . . type di-, tri or multiblock copolymers having one polyolefin block (A) and at least one polar or polyethylene-like polymer block (B and/or C).
It is moreover an aim of the present invention to produce B-A-B or . . . -C-B-A-B-C- . . . tri-, penta- or multiblock copolymers having a central polyolefin block (A) flanked on each side by at least one other polymer block, either polar or nonpolar (B and/or C).
It is moreover an aim of the present invention to provide polymers that can be used as compatibilizers for blends of polyolefins (e.g. iPP) with polar polymers such as polycarbonate or nonpolar polymers such as PE.
One or more of these aims are obtained by the process according to the present invention.